1. Field of Invention
The present invention relates to a method of processing a digital image, and particularly to a method extracting a textual area in a digital image.
2. Related Art
A content enriched digital image typically comprises figure areas, textual areas, continuous pictorial areas and the like. In processing such a digital image, different areas are generally processed in individual manners corresponding thereto. To enable all the areas in the digital image to be recognized, the figure areas and the textual areas are often endowed with clear edges, particularly for the textual areas, so that they can be discriminated for some specific uses. However, portions other than the edges of the figure and textual areas are not critically demanded since they may be presented in a not very clear result. On the other hand, images in the pictorial areas are quite demanding since they should be presented very clearly. In an application of printing the digital image using a carbon powder mode, the digital image is wholly weakened and thus the figure, textual and pictorial areas are all concurrently weakened. At this time, the presented effect of the pictorial areas is inclined to be insufficient and the edges of the figure and textual areas may lack sharpened or higher contrasts.
While being printed by use of a digital photostat, an original document is first scanned and then processed by a scanning unit in the digital photostat. After it has been processed, the original document is conversed into a grey-leveled or RGB-formatted image. Next, the image is further processed by, for example, the drivein a single bit or multi-bit manner. If the digital photostat is a color photostat, a screening step has to be executed to converse the 8-bit grey-leveled or colorful digital image to a 1-bit or multi-bit digital image. Before this screening step is performed, a color matching step is required to be conducted. Some photostats perform the above screening function through a periodic matrix while the other photostats eliminate a moir effect by using an error diffusion. Although halftones presented through executing the screening function may benefit to processing an original image having continuous tones therein, the edges of the textual areas and the figure areas becomes smoother, i.e., the edges are smoothened, thus not clear enough.
Therefore, there is a need created to provide a method of automatically discriminating a range of a textual area in a digital image so that the textual or figure area may be processed separately and endowed with clear and sharp edges while a pictorial area, having continuous tones and halftones in the digital image, may be filtered and smoothened and a smoother pictorial area may be obtained.